Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/10—Sintering only
  • B22F3/11—Making porous workpieces or articles
  • B22F3/1121—Making porous workpieces or articles by using decomposable, meltable or sublimatable fillers
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
  • C22C1/058—Mixtures of metal powder with non-metallic powder by reaction sintering (i.e. gasless reaction starting from a mixture of solid metal compounds)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

• the present invention relates to a method for the reactive sintering of a metal with a plastic material carried out in a vacuum atmosphere or a protective gas resulting in a porous material.
• the closest known method to the proposed invention is the so-called "Space holder method", in which besides the metal powder, a second material (including plastics) is used to maintain the free space in the pressing process.
• a second material including plastics
• the additional material must be completely removed by pyrolysis, dissolved or otherwise removed.
• the resulting porous compact is then sintered. As a result, a porous metal sinter is obtained.
• the plastic used in this technique is completely disintegrated into gaseous particles by pyrolysis.
• the plastic is intended not only to maintain the free space.
• the pyrolysis of the plastic material with the release of active carbon occurs and the particles are deliberately released. These substances are pores, react with metal to form carbides and other compounds. As a result, a porous metal sinter with porosity is obtained in which the walls are covered with carbides and additional particles.
• Control of the amount of plastic introduced, its type (plastic modification) and additional particles (particles introduced into the plastic prior to sintering in the process or to the metal mix at the mixing step) allow control of the surface reactivity of the sinter inside the sinter.
• the proposed technique is simpler than the Space holder technique. It is necessary to prepare the powder mixture then press and sinter without the additional time and laborious removal of the material that maintains the free space. From the point of view of the final product, the resulting material in the "reactive sintering" process is completely different from the product obtained by the "space holder” process.
• the "Space holder” method in a typical embodiment is GB714560 (A). Plastics that are completely degraded by gas products during pyrolysis (such as polyolefins) are used. The advantage of this solution is that the plastic is completely removed and does not contaminate the sintered material.
• plastic materials are used which, by pyrolysis, disintegrate into gaseous products and carbon particles.
• the resulting carbon particles are chemically active and react with the sintered metal to form a layer of carbides.
• suitable sintering parameters it will be possible to leave some of the active carbon inside the pores to allow for the creation of advanced materials such as chemically active filters (in this particular solution, the fiber particles in the form of fibers will be beneficial so as to provide controlled pore openness and the length of the path it will need. Medium to flow through the designed porous material).
• the essence of the invention is a method of reactive sintering of a metal with a plastic in which the metal particle input material of their alloys or mixtures and plastics or their modifications disintegrate as a result of the pyrolysis of active carbon is firstly mixed to form a homogeneous mixture.
• the advantage of this stage is that it is possible to compress under standard conditions using hydraulic presses at the processing temperature of the plastic used.
• the compactor obtained after pressing may have dimensions of the final product or larger for subsequent processing.
• the temperature and sintering time being selected depending on the metal used so as to allow the particles to sinter and the sintering is carried out under a vacuum atmosphere or protective gas.
• sintering there is pyrolysis of plastic with the release of active carbon and other substances.
• the resulting reactive carbon reacts with the metal particles to form its carbides and penetrates into the metal structure.
• the pores formed inside the metal sinter have a controlled controlled reactivity depending on the materials used, sintering time and temperature.
• the mixing step is carried out in a protective atmosphere.
• a protective atmosphere it is envisaged to incorporate in the prepared mixture of metal or ceramic rods or fittings to enhance the strength and to impart the desired properties to the finished product.
• additional elements rods, pipes, they should be precisely introduced into the compacts at the ironing stage.
• the particles are to be inside the pipe, it will form a mold. It is also advantageous when the input material in the form of metal particles, their alloys or mixtures is in the form of grains, tiles or fibers in proportions consistent with the expected final sinter parameters.
• the process can use particles of both pure metals (all known), their alloys and mixtures. It is preferable to add modifiers or additional particles of ceramics or chemical compounds in the form of grains, platens and fibers in the proportions necessary to achieve the desired sintered final parameters during the mixing step.
• the purpose of such treatments is to influence the sintering process (temperature expansion, gas emission, softening temperature, pyrolysis process, etc.) and final product properties (open / closed pores, oxides and other compounds, introduction of special particles with special properties).
• the advantage of the method of the invention is that it can utilize particles of all known plastics and their modifications which pyrolysis produce active carbon particles and other solids such as, for example, polycarbonate. It is significant that the process is not suitable for plastics which, as a result of pyrolysis, are totally gasified (polyolefin).
• the resulting sinter consists of the metal used, its carbides and additives added to the sint intentionally or as a result of the chemical reaction of the substrates.
• the dimensions of the pores and their distribution within the sinter is closely related to the particle size (in grain, platelet, fiber) particle size used and the particle size (in the form of grains, tiles, fibers) of the sintered metal.
• the surface of the sinter and pores inside the material is enriched in carbon or metal- coated carbide, particles introduced into the material prior to sintering and substances that are the products of the chemical reactions of the substrates.
• Fig. 1 is the XRD spectrum of the sinter surface after sintering of the titanium particle and PC polycarbonate particle;
• Figure 2 - SEM images of the sinter in four shots;
• Fig. 3 Measurement of microhardness of grinded surface of sinter and
• Fig. 4 Photo of Ti + PC sintered (20% by weight) using different size PC particles ⁇ 200 ⁇ a) 200 ⁇ 400 ⁇ b) 400 ⁇ 630 ⁇ c)
• This material can be used as a biomaterial because TiC titanium carbide is biocompatible. Sintering of Ti (titanium) powder with PC Powder (polycarbonate).
• the compact After sintering, the compact is coated with a black layer of TiC carbide / active carbon. Dimensions of the moldings remain unchanged (not for samples with more PCs made in other tests - platelets have undergone plastics decay). After sanding the top layer, the surface of the pure Titan, the carburized area and the edges of the mold and the thin layer of carbide / active carbon inside the pores are exposed. The weight of the molded parts after sintering was reduced by about 10%) compared to the weight of the moldings before sintering. The reason for this phenomenon is the escape of some of the PC pyrolysis reaction products in the form of gases.
• the invention may be applied.
• various fields such as light constructions, mechanical and acoustic damping, impact energy absorption, biomedical (implants), filters (particle filters / chemically active filters), chemical active devices (catalysts, reactors, sensors) (Tensile and conductive) or sensor production.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)

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Citations (3)

• 2016
  • 2016-11-17 PL PL419503(22)20161117A patent/PL238112B1/pl unknown
• 2017
  • 2017-11-15 WO PCT/IB2017/057137 patent/WO2018092037A1/en not_active Ceased

Patent Citations (3)

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